Rapid transesterification of cellulose in a novel DBU-derived ionic liquid: Efficient synthesis of highly substituted cellulose acetate.

Cellulose acetate (CA) is one of the most important cellulose plastics that has demonstrated extensive applications in many areas. In search of a more sustainable and efficient way to prepare CA, we synthesized a novel ionic liquid, [DBUC]Cl, based on the commonly used catalyst DBU (1,8-diazabicyclo[5.4.0]undecyquin-7-ene) in a simple manner. [DBUC]Cl can dissolve cellulose more efficiently than the same type of imidazolyl ionic liquid, owing to the stronger alkalinity of DBU. It is noteworthy that highly substituted CA (DS = 2.82) was successfully synthesized via transesterification with alkenyl ester under mild conditions (80 °C, 40 min) without the addition of a catalyst in this solvent, which is superior to most of the reported work. Furthermore, we confirmed that the synthesized CA had good thermoplasticity, and a transparent cellulose acetate film (CAF) was obtained by hot pressing with a small amount of glycerol. Therefore, we propose a new DBU-derived ionic liquid, which may serve as a versatile platform system for producing cellulose-derived bioplastics more sustainably and efficiently.